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<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Array Cardio 💪</title>
</head>
<body>
  <p><em>Psst: have a look at the JavaScript Console</em> 💁</p>
  <script>
    // Get your shorts on - this is an array workout!
    // ## Array Cardio Day 1

    // Some data we can work with

    const inventors = [
      { first: 'Albert', last: 'Einstein', year: 1879, passed: 1955 },
      { first: 'Isaac', last: 'Newton', year: 1643, passed: 1727 },
      { first: 'Galileo', last: 'Galilei', year: 1564, passed: 1642 },
      { first: 'Marie', last: 'Curie', year: 1867, passed: 1934 },
      { first: 'Johannes', last: 'Kepler', year: 1571, passed: 1630 },
      { first: 'Nicolaus', last: 'Copernicus', year: 1473, passed: 1543 },
      { first: 'Max', last: 'Planck', year: 1858, passed: 1947 },
      { first: 'Katherine', last: 'Blodgett', year: 1898, passed: 1979 },
      { first: 'Ada', last: 'Lovelace', year: 1815, passed: 1852 },
      { first: 'Sarah E.', last: 'Goode', year: 1855, passed: 1905 },
      { first: 'Lise', last: 'Meitner', year: 1878, passed: 1968 },
      { first: 'Hanna', last: 'Hammarström', year: 1829, passed: 1909 }
    ];
    inventors.forEach(inventors => inventors.years = inventors.passed - inventors.year);
    const people = [
      'Bernhard, Sandra', 'Bethea, Erin', 'Becker, Carl', 'Bentsen, Lloyd', 'Beckett, Samuel', 'Blake, William', 'Berger, Ric', 'Beddoes, Mick', 'Beethoven, Ludwig',
      'Belloc, Hilaire', 'Begin, Menachem', 'Bellow, Saul', 'Benchley, Robert', 'Blair, Robert', 'Benenson, Peter', 'Benjamin, Walter', 'Berlin, Irving',
      'Benn, Tony', 'Benson, Leana', 'Bent, Silas', 'Berle, Milton', 'Berry, Halle', 'Biko, Steve', 'Beck, Glenn', 'Bergman, Ingmar', 'Black, Elk', 'Berio, Luciano',
      'Berne, Eric', 'Berra, Yogi', 'Berry, Wendell', 'Bevan, Aneurin', 'Ben-Gurion, David', 'Bevel, Ken', 'Biden, Joseph', 'Bennington, Chester', 'Bierce, Ambrose',
      'Billings, Josh', 'Birrell, Augustine', 'Blair, Tony', 'Beecher, Henry', 'Biondo, Frank'
    ];
    
    // Array.prototype.filter()    筛选通过条件的所有元素
    // 1. Filter the list of inventors for those who were born in the 1500's
    // 筛选 出生在十五世纪

    let ans1 = inventors.filter(inventors => inventors.year >= 1500 && inventors.year <1600);
    console.table(ans1);

    // Array.prototype.map()
    // 2. Give us an array of the inventors first and last names
    // map和forEach区别
    // forEach()会修改原来的数组。而map()方法会得到一个新的数组并返回
    // forEach 针对每一个元素提供的函数
    // map 创建一个新数组，其中的每一个元素由调用数组的每一个元素的提供的函数得来

    let ans2 = inventors.map(inventors => inventors.first + ' | ' + inventors.last);
    // let ans2 = [];
    // inventors.forEach(inventors => ans.push(inventors.first + ' | ' +inventors.last));
    console.table(ans2);
    
    // Array.prototype.sort()
    // 3. Sort the inventors by birthdate, oldest to youngest
    // 稳定排序 不稳定排序
    // 两个数值一样应该维持原本的顺序
    let ans3 = inventors.sort((a,b) => a.year - b.year) //从小到大
    console.table(ans3);

    // Array.prototype.reduce()
    // 4. How many years did all the inventors live all together?

    let total = inventors.reduce((total,inventors) =>{
      return total + inventors.passed - inventors.year;
    },0) // ,0表示初始值
    console.table(total);

    // 5. Sort the inventors by years lived
    let ans5 = inventors.sort((a,b) => (a.passed - a.year) -(b.passed - b.year));
    console.table(ans5);
    // 6. create a list of Boulevards in Paris that contain 'de' anywhere in the name
    // https://en.wikipedia.org/wiki/Category:Boulevards_in_Paris

    // let res = [];
    // document.querySelectorAll('.mw-category-group li a').forEach((a) => res.push(a.title))
    // let de = res.filter(title => title.indexOf('de') !== -1)

    // 7. sort Exercise
    // Sort the people alphabetically by last name
    // 按 last name 字母顺序 
    let ans7 = people.sort((a,b) =>{
      // 解构
      let [aLast,aFirst] = a.split(', ');
      let [bLast,bFirst] = b.split(', ');
      return aLast > bLast ? 1 : bLast > aLast ? -1 : 0;
    })
    console.table(ans7);
    // 8. Reduce Exercise
    // Sum up the instances of each of these  统计出现次数
    const data = ['car', 'car', 'truck', 'truck', 'bike', 'walk', 'car', 'van', 'bike', 'walk', 'car', 'van', 'car', 'truck' ];
    let ans8 = data.reduce((obj,item) =>{
      if(!obj[item]) obj[item] = 1;
      else obj[item] += 1;
      return obj;
    },{});
    console.table(ans8);
</script>
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